Window blind



April 1959 c. w. MCCORMICK 2,882,563

wmnow BLIND Original Filed May 12, 1949 Q 2 eetsee l S SUN AT I 00 PM. P

I v v II! L6. V E I 0 SUN AT Noob z a{ V uhl AT H200 AM. I '1 g] L SUN AT [0:30 INVENTOR Charles M Ma Connie/r.

ATTORNEY April 21, 1959 c. w. MCCORMICK 2,382,563

wmnow BLIND Origipal Filed May 12, 1949 Y I 2 Sheets-Sheet 2 I I I V IVENTOR v Charles 14 M0 Cormz'cx.

United States Patent WINDOW' BLIND Charles W. McCormick, Meriden, Conn., assignor of one- 7 half to Merrill Ii. Steward, New Haven, Conn.

2 Claims. (Cl. 20-63) This invention relates to light control means by which the'light entering arooin, and the angle or time at which it enters such room, may be controlled. More particularly it'relates to means for controlling the natural daylight entering a room, and especially to means for controlling the period during a day in which sunlight is permitted to passdirectly through a window or windows into such room. This application is a division of application Ser. No. 92,933, filed May 12, 1949, now Patent No. 2,749,581, granted June 12, 1956.

One fsofthe chief problems encountered in the design of school buildings, ofiices, studios, factories and similar buildings, in which occupants normally maintain a relatively fixed position during their working hours, has been that of providing proper illumination, both natural and artificial, in order to prevent eyestrain and to promote maximum working efficiency. Natural daylighting of such rooms is generally preferred and is normally utilized to the maximum extent possible. One of the principal disadvantages in the use of natural light, however, is the fact that over certain periods of the day, depending on the geographical location of the building and the particular window exposure, rays of the sun pass through the window and'fall directly onto desks, tables or other working surfaces in the room, thereby producing a highly undesirable glare which is extremely fatiguing to anyone required to work under such conditions. Furthermore, the sunlight may enter the room at such an angle as to strike the occupants face-on, thus blinding them and making work impossible.

' Numerous means have been adopted to overcome this difliculty, some of the more common devices being roll shades, curtains or Venetian blinds on the inside of the windows, or awnings of various types on the outside of the windows, for example. Generally these devices, however, not only exclude the undesired direct rays of the sun, but also much, if not all, of the indirect sky light which is desired to give sufiicient illumination. This is particularly true of the roll shade and conventional awning, for example, where in both instances a direct barrier is interposed not only to the suns direct rays but to all other external light as well, requiring the illumination in the room to be supplemented by artificial light in many cases.

Some attempts have been made in the prior art to provide light control means which are effective to intercept the direct rays of the sun without, at the same time, shutting out too much of the natural indirect light. At best, a compromise. has been achieved, as in the conventional horizontal slat or louvered Venetian blind, for example, in which a considerable portion of indirect light is sacrificed in order to get satisfactory sunlight control. Moreover, devices of this type are attended by the further disadvantage that they must be periodically adjusted during the day to give the desired light control, and unless the adjustment is made at regular intervals during the day'by someone having a knowledge of proper illumination requirements, the result is quite apt to provide no re al improvement at all.

In addition to the foregoing disadvantages, external awnings of the slatted type, which have sometimes been It is a purpose of the present invention, therefore, to 1 provide a simple but effective means for controlling the natural light which is permitted to enter a room.

More especially, it is a purpose of the invention to provide means which will exclude the direct rays of the sun for any desired period or periods of the day, without, at the same time, shutting out the indirect or sky lighting (i.e. diffused light) necessary for eifective illumination of a room.

In general, the light control device of the present invention comprises a plurality of thin, slat-like louvers arranged in spaced parallel alignment across the face of a window or Windows, the louvers being disposed vertically and extending downward from the top of such window or windows. By this arrangement, the face of the window is, in effect, divided into a series of parallel, vertical lighttransmitting passages. For any particular building of given latitude above or below the equator and for any particular window exposure (i.e., north, south, east or we'st),lthe spacing of the louvers, their width and angular position with respect to the plane of the window are so correlated by the teaching of the present disclosure that the direct rays of the sun during the latters travel from horizon to zenith and back are intercepted by the slatlike louvers during a predetermined period of the day.

Thus, by way of example, a window facing a southerly,

out any adjustment. That is to say, a single period or several periods of excluding the direct sunlight at selected timesof the day may be-provided. Also, once the proper correlation of the above factors of louver spacing, width and angular setting has been determined, a design may he arrived at which makes adjustment of the blind unnecessary throughout an entire year even with changes in declination of the sun which occur during that time.

In the use of blinds of the present invention, unlike those of the types now commonly used, the view horizontally out of a window is not completely shut ofi from all positions in a room. This allows occupants positioned in a room, such as a schoolroom, for example, to have normal view out of at least one window in the room from their respective positions, and naturgl daylight is, of course, permitted to enter in the same direction. Following out the example of the schoolroom farther, it will be apparent from what has already been said that by proper design, the blind may be constructed to interceptthe passage of direct light from all angles within the horizontal are through which the sun travels during a particular period of the day, while still leaving unimpeded the entrance of light from angles outside this given arc. It is possible, also, to employ the blind for controlling sky glare alone, as on the north side of a building located in the northern hemisphere, where entrance of direct rays of the sun is not encountered. In such use, the design of the blind is alfected only by the requirement of preventing sky glare within an are on either side of thenormal forward line of sight of the person seated in the room, which is considered consistent Patent P 2 2 with good lighting practice. Commonly, direct light entering within an arc of aboutlS on either side of such forward line of sight has been deemed undesirable for good lighting conditions.

A still further feature of the invention is the provision of simple frame means for supporting a plurality of the louvers, whereby the latter are easily and economically assembled into blinds of any desired size, and the desired correlation of the spacing and angular setting of the louvers within the frame may be readily effected. A particular problem heretofore encountered in blinds of the slat or louver type has been their relatively high cost o-f production, due largely to the rather complicated methods employed in mounting the slats or louvers. The blinds or shutters herein disclosed obviate these disadvantages, while at the same time providing a structurally strong unit capable of withstanding considerable abuse. Furthermore, the construction is such that rattling of the louvers in a wind is effectively prevented. The louvers may be made of any suitably stitf material such as wood, metal or plastic. They may either be plane, or they may be made convex, or of other nonplanar configuration, if desired, to give added strength. In any event, it is desirable that they be as thin as possible to reduce to a minimum the impedance of light entering from desired directions and, correspondingly, the interference with vision in directions parallel to the planes of the louvers. Also, the louvers may be completely opaque, or, in some instances, it may be desirable to make them of translucent material such as a plastic to provide a diffused light transmitted through the louvers in addition to that reflected from the louver surfaces.

Other objects and advantages of the invention will be apparent from the following description of particularly suitable commercial installations embodying the principles of the invention, and shown in the accompanying drawings.

In the drawings Fig. l is a view in elevational perspective of a typical installation of two blinds embodying the present invention;

Fig. 2 is a partial view in plan looking down on top of one of the blinds shown in Fig. l; 3

Fig. 3 is a fragmentary view in side elevation showing details of means for mounting the blind;

Fig. 4 is a view taken on line 44 of Fig. 3;

Figs. 5, 5A, 5B and 5C are fragmentary views in plan of sections of the blind showing various angular settings of the louvers;

Figs. 6 and 7 are diagrammatic views in plan showing angles of light interception.

A typical installation of the novel light-controlling blinds is shown in Fig. l in which blinds are installed in'windows adjacent the corner of a room. The blinds of each window in this instance are composed of two independent sections, an upper section 21 and a lower section 22. Each section consists essentially of a plurality of thin metal slats or louvers 23 held in spaced, vertical alignment across the face of the window upon a pair of rods 24, 25 adjacent the upper and lower ends, respectively, of the louvers. In the preferred embodiment here shown, the louvers are slightly convex across their width so as to afford greater rigidity transversely of their length. As shown more particularly in Figs. 2, 3 and 4, each louver 23 is provided with apertures 26, 27 adjacent its upper and lower ends respectively through which rods 24; 25 pass to support the louvers. The louvers are held in their spaced parallel relation by spacing sleeves 28 on rods 24 and 25 between adjacent louvers 23. These spacers are of small cross sectional area to reduce the impedance of vision through the blind to a mlnimum. As seen best in Fig. 4, the spacers are of just sufiicient size to cause them to engage opposite margins of the apertures 26, 27. Rods 24 and 25 are threaded at their ends and are provided with looking washers 29 and locking nuts 30 by which the louvers 23 and the spacing sleeves 28 are held as a unitary assemblage between the locking nuts at each end of the rods. Rods 24 and 25 are made sufficiently long to extend somewhat beyond the sides of the windows and engage suitable brackets secured to the window frame by which the blinds are supported in position in front of the windows. As shown in Fig. 2, upper rod 24 is pivotally supported at its opposite ends in brackets 31 which are secured to the window frame and project outwardly therefrom. An outer retaining nut 32 and flat washers 33, between which the ends of the brackets are engaged, serve to retain the blind in position while permitting it to be hinged upon brackets 31. Lower rods 25, as shown in Fig. 3, are similarly provided with lock washers and nuts 29, 30, respectively, for holding the assemblage of louvers and spacers as an integral unit at the lower end of the blind. The ends of rod 25 also project laterally somewhat beyond the sides of the windows and are provided with a sleeve 34 and outer retaining nut 35. Clips 36, having separable, spring jaws 36a, are secured to the sides of the windows so that when the blind is swung downwardly in its closed or vertical position, sleeves 34 pass between and are removably held between jaws 36a of respective clips 36. Should it be desired to have access to the window for raising or lowering it, for example, the blind may be grasped near its lower end, as by rod 25, and pulled outwardly to disengage the ends of the rod from spring clips 36, thus hinging the blind on rod 24 and brackets 31.

As shown in Fig. 2, spacing sleeves 28 are cut so that their end faces lie in parallel, vertical planes perpendicular to the longitudinal axes of rods 24 and 25. This arrangement positions louvers 23 so that each louver lies substantially in a vertical plane intersecting the plane of the window at a given common angle. As explained in greater detail hereinafter, in order to provide sunlight control for a given installation over selected periods during the day, it is necessary to set the louvers in parallel vertical planes intersecting the plane of the window at a given angle. As shown best in Figs. 2, 3 and 5, the angular setting of louvers 23 is determined by cutting the ends of sleeves 28 at a given angle. When the louvers are assembled with spacers 28 upon rods 24 and 25, the louvers will of course be held in abutment with the end faces of the spacers by locking nuts 30, and are thus caused to assume the same angular setting as the ends of the sleeves. Sleeves 28 must of course be turned on rods 24 and 25 so that their end faces assume positions which lie in parallel vertical planes. Where the spacing sleeves 28 are generally rectangular in cross section, this positioning of the sleeves is more readily made than where the sleeves are cylindrical, although the latter may be employed satisfactorily if care is taken to see that they are rotated to their proper position on the rods.

In order to facilitate an understanding of the manner of designing a blind to effect the desired sunlight control for a particular installation, the following specific example is given as typical. A schoolroom in a building located on a parallel of latitude north of the equator has windows which face directly south. Normally, of course, direct sunlight will enter such a room during most of the day and it is desired to exclude the direct rays in order to reduce the possibility of causing eyestrain, as well as to eliminate unwanted, localized heating effects, while classes are in session. For the present example it is assumed that the classroom is unoccupied during a mid-day period extending from 11:00 am. to 1:00 pm. and that direct sunlight may be permitted to enter during this period. It is assumed also that the louvers available from which the blind is to be constructed are manufactured in a single width only. This being so, it is apparent that the control afforded by the blind must be effected entirely by the spacing and angular setting of the individual louvers within their supporting frame.

In the following description, and elsewhere in the present specification, a louver, in many instances, is spoken of as lying in a plane. It is apparent however that louvers having a convexity, or other non-linear form in transverse cross section, cannot actually lie in a single plane, and the term plane of the louvers is therefore used to mean the plane in which opposite longitudinal edges of the louvers lie, and as shown in Figs. 6 and 7 is designated plane L.

The proper spacing and setting of the louvers in the frames is determined by first measuring the azimuthal positions of the sun at the two limits of the predetermined period for which direct rays are to be admitted. This may be done by actual measurement or it may be calculated from data obtainable from standard sources. In this instance these limits have been assumed as 11:00 am. and 1:00 pm. and the angular position of the sun with respect to the plane W of the window at these two times is shown in Fig. 6. The variables of louver spacing and angular setting in the vertical axis are of course mutually dependent and change, for the same time lapse, with each different period of the day. One practical way of correlating these variables simply for a given installation is to plot the problem graphically, as in Figs. 6 and 7. As there shown, the spacing and angular setting is determined so that the diagonals lying in a plane perpendicular to the length of the louvers, when drawn between any pair of adjacent louvers, will intercept the azimuthal positions of the sun at the respective limits of the period for which direct sunlight is to be allowed to pass through the blind. For most practical purposes, the diagonals drawn through the diagonally opposite edges of adjacent louvers may be used for plotting the desired spacing and angular setting. It will be apparent, however, that this is an approximation only and is not strictly accurate except where the louvers are plane. Where the louvers are of convex or of other cross-sectional shape, this assumption will no longer be correct, and the error introduced will depend on the amount of deviation in the surface of the louver from a plane. In such cases the diagonals drawn from the edges of one louver, at its concave side, tangent to the convex face of the louver adjacent that side, will determine accurately the angular limits in azimuth of maximum intensity of direct light transmission for that particular form of louver.

Figs. 6 and 7 are of course purely diagrammatic since, for all practical purposes, the distance of the sun from the plane of the window may be considered as infinite. For this reason, it will be seen that for any given position of the sun, the difference in the angle a measured in azimuth between plane W and lines drawn from the sun to any point on or closely adjacent the surface of the Window will be so negligible that it may be completely disregarded. The same is true with regard to angle 0. All the louvers in a blind may therefore be set in their vertical axes at the same angle with respect to plane W without introducing any appreciable error. Since the example here given assumed that the window faced due south, it will be seen that the planes L of the louvers in this instance Will be at right angles to plane W and, since the sun moves 15 in each hour, the angle b formed at the intersection of the aforesaid diagonals will be 30. Should it be desired to permit direct rays to enter only between 11:30 am. and 12:30 pm. for the same window, the spacing of the louvers should be adjusted so that the angle of intersection of the diagonals is 15; that is, the spacing of the louvers in this case would be just half of that in the preceding example.

As a further example, assume that entrance of direct sunlight is to be permitted during a morning recess period lasting from :00 am. to 10:30 am. Again the angular position of the sun with respect to plane W of the window is determined for each of these two times and the spacing of the louvers is adjusted to make the diagonals drawn through opposite edges of adjacent louvers coincide with these angles. If the windowis again assumed to be facing due south, it will be seen, as shown in Fig. 7, that in this instance the planes L will no longer intersect plane W at right angles but at some other angle depending upon the exact meridian of longitude onwhich the building is located. The blind can'of course be adapted for windows having any exposure from which direct rays of the sun can enter, the spacing and angular setting of the louvers in each instance being such that the diagonals drawn through the opposite edges of adjacent louvers coincide, respectively, with the lines drawn from the particular window to the sun's position at the limits of the desired period.

In the foregoing examples, it has been assumed that the width of the louvers which were available was fixed, it being desirable from economical considerations to limit the number of different widths in which the louvers are manufactured. Obviously, however, louvers of various widths may be employed and the spacing adjusted accordingly. Additional factors which must be considered in this connection are the fact that more louvers of a narrow width will be required to effect the desired control than will be needed where louvers of greater width are employed; that is, the spacing between adjacent louvers will decrease proportionately to the decrease in width of the louvers employed for any given sunlight control problem. And generally speaking, the greater the number of louvers used, the greater will be the effect of impairing the vision through the blind, even in directions parallel to the planes of the louvers. Furthermore the width has, of course, a direct effect upon the stiffness or rigidity of the louver.

It has been found in practice that a louver having a width of about 2 inches, and having a convexity of about one-sixteenth to three thirty-seconds of an inch at the midpoint, is generally suitable for most purposes. Louvers made of aluminum alloy are particularly suitable for use in a blind of the present construction, since it is practical to employ relatively thin sheet stock of such alloy in producing the louvers. For example, sheet stock having a thickness of 0.010 inch is quite suitable, especially where the completed louver is made with the slight convexity suggested above and illustrated in the drawings. This provides a louver of extremely light weight and sufficient flexibility for such slight accommodation as may be necessary when it is installed in its supporting frame, without at the same time having it subject to the disadvantages of insufficient rigidity and undesirable bending and flexing due to drafts coming in an open window. Other widths, thicknesses and convexity may, of course, be used, those mentioned above being merely typical of what has been found practical in good commercial practice.

Consideration must also be given to the problem of preventing undesirable glare by reflectance from the louver surfaces themselves. This may usually be controlled conveniently by painting, etching or otherwise finishing the surfaces of the louvers with a flat or matte finish to effect a diffusion of the light striking these surfaces. In some instances, visibility characteristics may be improved by providing the louvers with a tinted surface, as for example with a pale green surface color. And where the louvers are convex in cross section, they should be positioned in their supporting frame so that the concave surface is directed away from the occupants in the room, in order to avoid annoyance from internal reflection between adjacent louvers.

From the foregoing general considerations, it will be apparent that various specific modifications may be made in the construction of the blind here disclosed without departing from the inventive concept of the present invention. Quite obviously also, the blinds may be made in a single section instead of the two sections shown in Fig. 1,. ,It is apparent therefore that the invention is not limited to the specific example illustrated and described above, but is susceptible to such other modifications and changes as fall within the scope of the appended claims.

What is claimed is:

1. A blind for controlling the light permitted to enter a room through a window, which blind comprises a plurality of louvers vertically disposed in spaced arrangement and formed of thin strips of stifi but flexible sheet material of convex transverse section, each of said strips being apertured adjacent each end, a positioning rod extending through said apertures adjacent each end, respectively, for supporting said louvers, and spacers carried on said rods intermediate adjacent louvers, said spacers being of small cross-sectional area and engaging at their ends the margins of the apertures in said louvers, the respective end faces of said spacers being disposed in parallel planes, and retaining means on said rods for pressing said spacers against said louvers to retain the latter in said parallel planes; said blind having brackets for securement to the upper margin of said window, and one of said positioning rods being pivotally supported by said brackets to suspend said blind in front of said window and to permit swinging movement of the lower end of said blind away from said window about said one rod as an axis.

2. The combination, as defined in claim 1, wherein said blind is provided with clips for securement to the lower margin of said window and within which the other positioning rod adjacent the lower end of said blind is adapted to be yieldingly engaged.

References Cited in the file of this patent UNITED STATES PATENTS 1,979,808 Mussbach Nov. 6, 1934 2,015,342 Indahl Sept. 24, 1935 2,485,263 Digby Oct. 18, 1949 2,552,406 Chartofif May 8, 1951 2,749,581 McCormick June 12, 1956 Chm-num- 

